URLDate
Verified		Extra Software
Requirements
(if any)		Access
Conditions		Notes
http://dx.doi.org/10.1016/0261-2194(87)90068-8DOI Link
http://ac.els-cdn.com/0261219487900688/1-s2.0-0261[...]08/08/2013PDF ReaderItem is within a limited-access website
http://www.sciencedirect.com/science/article/pii/0[...]12/15/2016PDF ReaderItem is within a limited-access website